Wireless telecommunications providers often find it useful in attracting new subscribers to subsidize the prospective subscribers' purchase of a handset. The cost of the handsets, which are complex and sophisticated devices, would otherwise fall to the subscribers. A subsidy lowers the financial barrier to the new subscriber's entry into the domain of wireless communications. Although this is a desirable outcome for new subscribers, for such a proposition to be economically viable for the wireless network operator, it must lead to an assured financial return. The service provider, for example, might seek a guarantee that, for a certain period of time, the subscriber's wireless access would be provided only by the network operator offering the subsidy. In return for subsidizing the handset, the network operator would recoup that expense in the form of subscriber air time during the period of exclusivity.
The question arises, however, as to how a network operator can ensure that a subscriber using one of its subsidized handsets has access only to that network's services. One approach to this problem has been to limit the subscriber's access to services, when using the subsidized handset, to those offered by the particular operator by conditioning the use of the handset on its being "unlocked" only for that service. An example of this type of "locking" mechanism has been developed that is compatible with standards promulgated by Groupe Special Mobile ("GSM"), a European organization responsible for developing wireless telecommunications standards that have been adopted in approximately 60 countries as of the filing of this document. (Throughout this document, GSM and certain terms it has defined are referred to for purposes of illustration only. The implementation of methods and apparatus according to the present invention does not depend upon this standard, but could be used with other telecommunications standards, including those that presently exist or are yet to be developed).
An existing approach to mobile telecommunications handset locking utilizes a subscriber identification module ("SIM") specific to the network operator offering the subsidy. A SIM may take the form of a card incorporating an integrated circuit and memory in which subscriber information including a network identification symbol is stored. In the context of GSM, for one example, the network identification symbol is included as a subset of an International Mobile Subscriber Identification ("IMSI"). An IMSI is a globally unique number, recognizable by the GSM telephone network operators, that has the following 15 decimal digit format:
______________________________________ 3 digits 2 digits 2 digits 8 digits ______________________________________ XXX XX XX XXXXXXXX MCC MNC HLR ID Rest of MSIN ______________________________________
As shown, an IMSI includes a 3 digit mobile country code ("MCC"), a 2 digit mobile network code ("MNC"), a 2 digit home location register identification ("HLR ID"), and an eight digit mobile subscriber identification number ("MSIN").
Wireless telephone equipment, on the other hand, is defined by an equipment identification number. Under the GSM system, for example, a handset is uniquely identified by an International Mobile Equipment Identification ("IMEI"). The structure and allocation principles of IMEIs are defined in GSM 03.03--version 3.6.0, published October, 1993. According to that document, an IMEI uniquely identifies a given item of mobile station equipment. The IMEI includes 15 digits, as shown immediately below:
______________________________________ 6 digits 2 digits 6 digits 1 digit ______________________________________ XXXXXX XX XXXXXX X TAC FAC SNR SP ______________________________________
The six most significant digits specify a type approval code ("TAC"), the contents of which are determined by a central decision-making body. The two next most significant digits comprise a final assembly code ("FAC"), which identifies the place of manufacture/final assembly of the equipment and is encoded by the manufacturer. The next six digits set forth the serial number of the equipment, uniquely identifying it within each TAC and FAC. Manufacturers are required to allocate individual serial numbers in sequential order. Finally, the IMEI includes a spare digit for further assignment.
In addition to permanently programming mobile telephone equipment with an equipment identification number, such as an IMEI, it is also known to permanently encode a mobile telephone handset at the time of manufacture with a code identifying a particular network. This network identification (NID) code (which, under GSM, is the two digit MNC) may be burned into or otherwise coded in a circuit within the handset. Preferably the NID is encoded in the handset in such a manner that it cannot be modified by another without destroying the product. Upon powering up, the handset is locked, and can be unlocked only by inserting the SIM into a receiving and reading slot in the handset. A processor in the handset is programmed to read the IMSI off the SIM, extract the MNC, and compare the MNC with an MNC value stored in the handset. If the NID (e.g., MNC) in the handset is matched by the NID (MNC) extracted from the subscriber information (e.g., IMSI) on the SIM, the handset unlocks itself, enabling the user to make regular telephone calls. A scheme of this sort is in use, for example, in the Orange system and the Mercury One-2-One system in the United Kingdom.
A major shortcoming with the foregoing approach, in which an NID in the handset is compared with one on the SIM, is that the handset must be customized at the time of manufacture for use with only one particular network. This limitation would preclude a service provider from buying handsets in bulk in order to supply them for use with different networks within its system. Compatibility with such entities as resellers of wireless network services would also be inhibited. One proposed solution to this problem is to program the handsets at the time of manufacture with a number of different NIDs. This approach, however, would be insufficiently flexible to account for an operator's establishment or acquisition of a further network, or for an operator's relationship with a reseller or another network operator.
No handset locking system has yet been provided that frees the handset from being locked to a particular end network or other entity at the time of manufacture. It has therefore been impossible to pre-lock wireless handset to SIMs associated with a particular service provider (e.g., one operating multiple networks), a particular network, a particular reseller, or even to lock a handset to a particular individual SIM. Moreover, it is not possible with existing systems to disable locking of individual handsets over the air, and possibly via the key board of the handset, on the occurrence of preselected conditions, such as when an initial subscriber contract period has expired. In addition, the existing approach does not permit the activation of a handset remotely (e.g., over-the-air). Nor dies it permit a device to be remotely re-locked (e.g., over-the-air) to a specific operator, network, reseller, or individual SIM. Among other difficulties, these shortcomings impose constraints on the development and availability of wireless telephone services. New alliances between operators or resellers may arise that would make it desirable to permit the locking criteria to be changed, for example, but this is not possible with the existing approach.
An improved mechanism for locking handsets and other devices should be sufficiently robust to prevent individual subscribers from attempting to move their business to a rival operator. It must also withstand attempts at circumvention by criminals or unscrupulous dealers or operators. Furthermore, if the security of an individual handset is compromised, it is critical that the result should not be able to lead to the compromise of other handsets associated with the handset provider.
One of the unmet needs of conventional wireless communications systems is the ability to lock a handset to services provided only by a particular service provider, or to other network operators or resellers with which the particular operator has an agreement. In order to meet this need, it should be possible for handsets to be distributed to such designated service providers by one or more physical distribution centers (PDCs) run by the operator. To maintain security throughout this distribution process, the handsets must be pre-locked to prevent their use by any operator or re-seller other than those that are designated service providers. For convenience and economy, the handsets should be operable without the need to program them at a PDC prior to delivery. Any further steps required for activation of the handset should be capable of being performed remotely, for example, over-the-air, and then only by the operator or one of its designated providers.